1. Field of the Invention
This invention relates to an electrostatic latent image developing device capable of converting an electrostatic latent image to a visible image with the aid of a toner containing magnetic material.
2. Description of the Prior Art
Various kinds of developing devices have heretofore been proposed to hold and move a toner containing magentic material and cause it to act upon an electrostatic latent image produced on an electrostatic latent image holding member, for example, a record medium, a drum-shaped photosensitive screen etc. so as to convert the electrostatic latent image to a visible image.
Such developing device, however, has the drawbacks that an electrostatic latent image having a relatively low electric potential of the order of lower than 200 V or dot-shaped electrostatic latent image could not be converted to a picture image having a good graduation.
In addition, since the moving speed of the toner is lower than the travelling speed of the electrostatic latent image produced on its holding member, there is a risk of a black picture image being spattered with the toner caused by presence of a heap of toner particles and being eventually subjected to overdevelopment.